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Increased global functional connectivity correlates with LSD-induced ego dissolution

Authors: Enzo Tagliazucchi, Leor Roseman, Mendel Kaelen, Csaba Orban, Suresh D Muthukumaraswamy, Kevin Murphy, Helmut Laufs, Robert Leech, John McGonigle, Nicolas Crossley, Edward Bullmore, Tim Williams, Mark Bolstridge, Amanda Feilding, David J Nutt, Robin Carhart-Harris.

 

About the study:

This brain imaging study shows that LSD increases integration of information by enhancing functional connections (“communication”) between different brain systems. This includes new patterns of communication beyond the constraints of anatomical connectivity, thus enabling regions that are not wired to communicate, to communicate.

Importantly, these effects correlated with changed consciousness, specifically self-reported ‘ego-dissolution’ – the loss of a ‘sense of self’ and feeling of ‘oneness’ with the world.

The findings suggests that LSD diminishes the functional identity of individual brain systems, resulting in the blurring of borders between the self and environment and other characteristic effects of LSD.

 

Abstract:

Highlights

  • High-level cortical regions and the thalamus show increased connectivity under LSD
  • The brain’s modular and rich-club organization is altered under LSD
  • Increased global connectivity under LSD correlates with ego dissolution scores

Summary

Lysergic acid diethylamide (LSD) is a non-selective serotonin-receptor agonist that was first synthesized in 1938 and identified as (potently) psychoactive in 1943. Psychedelics have been used by indigenous cultures for millennia [ 1 ]; however, because of LSD’s unique potency and the timing of its discovery (coinciding with a period of major discovery in psychopharmacology), it is generally regarded as the quintessential contemporary psychedelic [ 2 ]. LSD has profound modulatory effects on consciousness and was used extensively in psychological research and psychiatric practice in the 1950s and 1960s [ 3 ]. In spite of this, however, there have been no modern human imaging studies of its acute effects on the brain. Here we studied the effects of LSD on intrinsic functional connectivity within the human brain using fMRI. High-level association cortices (partially overlapping with the default-mode, salience, and frontoparietal attention networks) and the thalamus showed increased global connectivity under the drug. The cortical areas showing increased global connectivity overlapped significantly with a map of serotonin 2A (5-HT2A) receptor densities (the key site of action of psychedelic drugs [ 4 ]). LSD also increased global integration by inflating the level of communication between normally distinct brain networks. The increase in global connectivity observed under LSD correlated with subjective reports of “ego dissolution.” The present results provide the first evidence that LSD selectively expands global connectivity in the brain, compromising the brain’s modular and “rich-club” organization and, simultaneously, the perceptual boundaries between the self and the environment.

"These results help to inform not only on the neurobiology of the psychedelic experience but on a fundamental aspect of human consciousness, namely the sense of possessing a coherent “self” or “ego” that is distinct from others and separate from the external environment."

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